Pressure sensors are critical components in many applications such as tire pressure monitoring. Pressure sensors are typically molded in a package to ensure the pressure sensor works reliably over a wide range of temperature, humidity and load conditions. A typical pressure sensor package includes a pressure sensor die with a pressure inlet and a logic die such as an ASIC (Application-Specific Integrated Circuit). The logic die is electrically connected to the pressure sensor and processes the signals provided by the pressure sensor.
A conventional pressure sensor package includes pressure sensor and logic dies disposed laterally adjacent one another on a different regions of a substrate such as on different die pads of a lead frame, and electrical connections are made to the dies by wire bonding. The pressure sensor is mounted in a hole in the die paddle through which the pressure signal impinges on the active surface of the pressure sensor chip such as a piezo-active suspended membrane. The assembly is encapsulated with mold compound so that the pressure inlet remains open by the injection molding tool. Electrical connections protruding from the molded package are severed from the lead frame and bent so that board mounting is possible.
The pressure sensor die should be disposed within the package so as to be immune from mechanical impact of the assembly processes and the housing (package). Such buffering is desired because mechanical stresses on the pressure sensor chip cause the sensor membrane to move and thus generate an unwanted signal. Moreover, the influence of various substances from the environment may result in corrosive effects, which can particularly affect contact pads which typically have Al, AlCu or Cu surfaces that are contacted by bond wires. The contact pads of the logic die are especially vulnerable to corrosive effects, as a partly constant electrical voltage is applied to these pads and therefore are highly susceptible to electrochemically accelerated degradation. An improved pressure sensor package is needed which adequately addresses these issues, while also having a small size.